Area 88 (TV)

They are both animes dealing with airplanes. 

One in the sky, one in the sea - both about dealing with the harsh environment and who you can depend on. 

Both tell a story about betrayal from a close fake friend resulting in a life thretening situation. In Gankutsuou Dantes was betrayed and sent of prison out of jealousy and Shin, (main character of Area 88) and sent to war with low survival rates by a mean trick. Also, both stories contain a woman as a reason for betrayal. Difference: Area 88 isn't concentrated on revenge as much as Gankutsuou. 

Another excellent angsty military aviation series but this time set in an alternative world with a WWII feel to it.  

A three part military anthology, two of which are aviation in nature and all with a WWII focus with a classic Leiji Matsumoto look and feel. 

Epic dogfights although I think the ones in macross are better.